Introduction
In the realm of electrical engineering and safety, ensuring that insulating materials can withstand abnormal heat and fire due to internal electric effects is paramount. This is crucial for components necessary to retain current-carrying parts and those exposed to potential thermal stresses. One of the primary methods for verifying the resistance of these materials is the glow wire test, a standardized procedure detailed in IEC 60695-2 series.
Purpose of the Glow Wire Test
The glow wire test is designed to evaluate the ability of insulating materials to resist ignition and to prevent the spread of fire when subjected to high temperatures. These temperatures simulate the conditions that might occur due to overheating or electrical faults within a device. The primary objectives are to determine:
- Whether the component catches fire
- The duration of any combustion
- The potential for burning fragments to be released and spread fire
By understanding these factors, manufacturers can assess the fire safety of their components and ensure compliance with relevant safety standards.
Standards Governing the Glow Wire Test
The glow wire test is governed by several standards under the International Electrotechnical Commission (IEC) 60695-2 series, which include:
- IEC 60695-2-10: Describes the apparatus and general testing procedures.
- IEC 60695-2-11: Provides methods for testing finished appliances.
- IEC 60695-2-12: Details testing methods for solid electrical insulating materials.
- IEC 60695-2-13: Specifies testing methods for thermosetting molding materials.
These standards ensure a comprehensive approach to assessing various components and materials used in electrical devices.
Execution of the Glow Wire Test
The glow wire test involves heating a wire loop to a specified temperature, ranging from 550 °C to 960 °C, depending on the material and component being tested. The wire, simulating an overheated conductor, is then applied to the sample for a set duration. The specific procedures are outlined in IEC 60695-2-11:2014, which provides detailed guidelines on conducting the test.
Temperature Specifications
- 960 °C: For parts necessary to retain current-carrying components in position.
- 850 °C: For enclosures intended for installation in hollow walls.
- 650 °C: For all other parts, including those retaining protective conductors and enclosures mounted on non-combustible walls.
The test is performed on the material with the minimum thickness used in the component to ensure accurate results.
Alternative Tests for Small Parts
For small parts with surface dimensions not exceeding 14 mm x 14 mm, an alternative test, such as the needle flame test (IEC 60695-11-5:2016), may be used. This adaptation allows for practical testing of components where traditional glow wire testing may not be feasible.
Importance of the Glow Wire Test
Conducting the glow wire test is critical for several reasons:
- Safety Assurance: It ensures that insulating materials will not contribute to fire hazards, even under abnormal conditions.
- Regulatory Compliance: Adherence to IEC standards helps manufacturers comply with international safety regulations, facilitating market access in various regions.
- Performance Evaluation: The test provides insights into the effectiveness of flame retardants used in the materials, guiding improvements in product safety.
Conclusion
The glow wire test is a vital procedure for verifying the resistance of insulating materials to abnormal heat and fire due to internal electric effects. By adhering to IEC 60695-2 series standards, manufacturers can ensure their components meet stringent safety requirements, ultimately protecting users and preventing fire hazards in electrical devices.
